Optical waveguide means a medium for introducing a light wave. In order to make light transmit in a desired direction, the optical waveguide may have different shapes and structures. Currently, the main disadvantage of the heterogeneous integrated optical waveguide structure is that the light cannot be completely coupled from the passive waveguide to the active waveguide, therefore resulting in a mixed modal effect. The main disadvantage of the mixed mode is that the input light is unable to be efficiently used, therefore, it is difficult to be applied to a three-dimensional integrated circuit (3D integrated circuit) to be vertically integrated with other optical or electronic components.
In the manufacturing process, the heterogeneous integrated optical waveguide comprises a passive waveguide formed of silicon having a different shape of the structure on the silicon substrate, and then a heterogeneity integration of a III-V compound and the passive waveguide is performed after an alignment process. Because the passive waveguide structure is a submicron level structure, the difficulty in the alignment process is very high, and thus it cannot be 100% aligned with the current technology, so that the efficiency and quality of the heterogeneous integrated optical waveguide cannot be effectively improved.
It is therefore necessary to provide an optical waveguide structure and a manufacturing method thereof to completely couple the light from a passive waveguide to an active waveguide, to reduce the difficulty of the production process, and improve the accuracy in the alignment process, in order to solve the problems existing in the conventional technology as described above.